On the Noise Produced by a Propeller in Unsteady Rotational Motion

A number of recent studies have suggested that the unsteady rotational motion of

a UAV propeller can produce tonal noise. This paper describes a method for calculating this

noise source. The method is then used to predict the level of the noise produced by this

source for a typical small UAV propeller. The method is based on Farassat’s Formulation

1A and includes contributions from the thickness and loading noise sources. The unsteady

loading on the propeller blades is calculated using arbitrary motion theory. Experimental

results are also presented to support the calculations.